In order to properly demonstrate the specific binding or biological activities of an antibody, a reference antibody (i.e., a “control”) is necessary. Without proper controls, it is difficult to determine the specificity of binding or establish a causal relationship between the specific binding activity and the biochemical and biological effects of an antibody.
In general, two major types of control agents are in use for testing antibodies. The first control is the buffer that is used in the preparation of the testing antibody, such as phosphate buffered saline. The second type of control agent is an antibody that does not share the antigen specificity with the testing antibody. While the antibody control is clearly the better choice, it is far from ideal. This is due to the fact that while most of these antibodies do not recognize the antigen of interest, they retain fully functional complementarity determining regions (CDRs) and are fully capable for interaction with other antigen molecules. Such interactions often produce inexplicable experimental outcomes in the in vitro tests and in studies using animal models. In fact, it is not uncommon that a researcher moves from one control antibody to another until he/she comes across an antibody that gives the least background signals. Clearly, there is a great unmet need for improved, rationally designed control antibodies.